This application relates generally to the field of ultrasonic welding, and, more particularly, to cleaning ultrasonic welding tools.
Ultrasonic Welding (USW) is a joining technique for lap joints of two or more layers of the same or dissimilar metals, such as, for example, copper and aluminum. The layers or parts to be welded are placed in a fixed anvil and a moveable horn or sonotrode makes contact with the parts to be welded. Pressure is applied to keep the horn in contact with the welded parts, and to hold them together. The horn delivers ultrasonic vibrations that heat up the parts. The vibrations move either up-and-down or side-to-side, leading to the binding of the parts. The horn is retracted, and the welded parts can be removed from the anvil.
The anvil must grip and hold one of the parts stationary during the ultrasonic vibrations. The shear forces generated during a weld cycle can be significant, and if the anvil design or mounting allows any movement, the efficiency of the weld cycle is diminished. To this end, the anvil has a gripping or weld pattern machined onto its surface. A similar pattern, which is used for gripping, with high ridges and low valleys, is also present on the horn. When the vibrations begin, the anvil weld pattern seats into a part to be welded and prevents it from vibrating. The horn, which seats into the other part to be welded, causing the part to vibrate against the stationary part seated on the anvil.
During USW, the high-frequency vibration of the horn against the welding parts causes a buildup of metal powders in the weld patterns on the horn and the anvil, resulting in decreased weld strength, due to the altered weld pattern topography. The sharp edges of certain welding tool designs may lead to high buildup rates that require frequent cleaning of the welding tools.
Unfortunately, cleaning the horn and anvil usually necessitates removal of the horn and/or anvil from the USW fixtures, significantly slowing the manufacturing process, and increasing downtime and cost. In addition, removal and then replacement of the cleaned horn and anvil requires realignment and adjustment of the tools and fixtures. This readjustment introduces unpredictability to the USW process and adds to the associated downtime and cost.
It would be desirable to have an in-line cleaning method for maintaining the continuity of the USW process, while limiting variability, downtime, and cost.